perf(gb): allocate discard hands only on ting cache miss (#58)

Author: TypeThe0ry

src/main/java/top/ellan/mahjong/table/core/round/GbBotDecisionService.java

@@ -189,9 +189,15 @@ private DiscardChoice bestDiscardChoice(
         EnumMap<MahjongTile, GbTingResponse> tingMemo = new EnumMap<>(MahjongTile.class);
         for (int i = 0; i < hand.size(); i++) {
             MahjongTile discarded = hand.get(i);
-            List<MahjongTile> remaining = new ArrayList<>(hand);
-            remaining.remove(i);
-            GbTingResponse ting = tingMemo.computeIfAbsent(discarded, ignored -> tingEvaluator.evaluate(remaining, melds));
+            GbTingResponse ting = tingMemo.get(discarded);
+            if (ting == null) {
+                List<MahjongTile> remaining = new ArrayList<>(hand);
+                remaining.remove(i);
+                ting = tingEvaluator.evaluate(remaining, melds);
+                if (ting != null) {
+                    tingMemo.put(discarded, ting);
+                }
+            }
             DiscardChoice candidate = new DiscardChoice(i, readyScore(ting), discardPreference(hand, discarded));
             if (best == null || candidate.compareTo(best) > 0) {
                 best = candidate;

src/test/kotlin/top/ellan/mahjong/table/core/round/GbBotDecisionServiceTest.kt

@@ -24,7 +24,7 @@ class GbBotDecisionServiceTest {
 
         assertTrue(
             GbBotDecisionService.discardPreference(hand, MahjongTile.P9) >
-                GbBotDecisionService.discardPreference(hand, MahjongTile.M2)
+                GbBotDecisionService.discardPreference(hand, MahjongTile.M2),
         )
     }
 
@@ -33,14 +33,49 @@ class GbBotDecisionServiceTest {
         val service = GbBotDecisionService(8)
         val hand = listOf(MahjongTile.M1, MahjongTile.M2, MahjongTile.M3, MahjongTile.EAST)
 
-        val suggestedIndex = service.suggestedDiscardIndex(hand, emptyList()) { remaining, _ ->
-            if (MahjongTile.EAST !in remaining) {
-                GbTingResponse(true, listOf(GbTingCandidate("W1", 8)), null)
-            } else {
-                GbTingResponse(true, emptyList(), null)
+        val suggestedIndex =
+            service.suggestedDiscardIndex(hand, emptyList()) { remaining, _ ->
+                if (MahjongTile.EAST !in remaining) {
+                    GbTingResponse(true, listOf(GbTingCandidate("W1", 8)), null)
+                } else {
+                    GbTingResponse(true, emptyList(), null)
+                }
             }
-        }
 
         assertEquals(3, suggestedIndex)
     }
+
+    @Test
+    fun `discard suggestion evaluates the first remaining hand once per duplicated tile`() {
+        val service = GbBotDecisionService(8)
+        val hand = listOf(MahjongTile.M1, MahjongTile.M2, MahjongTile.M1)
+        val evaluatedHands = mutableListOf<List<MahjongTile>>()
+
+        service.suggestedDiscardIndex(hand, emptyList()) { remaining, _ ->
+            evaluatedHands += remaining.toList()
+            GbTingResponse(true, emptyList(), null)
+        }
+
+        assertEquals(
+            listOf(
+                listOf(MahjongTile.M2, MahjongTile.M1),
+                listOf(MahjongTile.M1, MahjongTile.M1),
+            ),
+            evaluatedHands,
+        )
+    }
+
+    @Test
+    fun `discard suggestion preserves null evaluator recomputation`() {
+        val service = GbBotDecisionService(8)
+        val hand = listOf(MahjongTile.M1, MahjongTile.M1, MahjongTile.M1)
+        var evaluations = 0
+
+        service.suggestedDiscardIndex(hand, emptyList()) { _, _ ->
+            evaluations++
+            null
+        }
+
+        assertEquals(hand.size, evaluations)
+    }
 }